[Unknown Mod][Spells] Tweaks to Earthquake spell

[LeHerosInconnu]

The damage inflicted by the Earthquake spell is related to the hero's spell power.
This makes the spell more predictable and more usable, putting it on a par with other spells.

For castle defense, these values are currently used:

• 2 hit points per wall section
• 1 hit point for each turret
• 1 hit point for the drawbridge
• 1 additional hit point per wall section when fortifications are built in the Knight's castle
• 1 hit point for the Ballista

This corresponds to a total of 16 hit points for the Knight's castle when the fortifications are built, and a total of 12 hit points for the other castles.

Consider that the Ballista can also be hit by the Earthquake spell.

Let's keep the hit point values for the Earthquake spell the same as for the catapult, also with the constraint of not creating additional graphics for damage to castle walls, etc., and assume that each point of the hero's spell power does 0.5 damage (rounded down for these initial damage).
Let's also randomly add 0 or 1 damage to the result obtained.
Also, the initial damage cannot be less than 1 damage.

This gives us:

• spell power 1, 0.5 damage = 1 damage + (0 damage or 1 damage) --> 1 damage or 2 damage
• spell power 2, 1.0 damage = 1 damage + (0 damage or 1 damage) --> 1 damage or 2 damage
• spell power 3, 1.5 damage = 1 damage + (0 damage or 1 damage) --> 1 damage or 2 damage
• spell power 4, 2.0 damage = 2 damage + (0 damage or 1 damage) --> 2 damage or 3 damage
• spell power 5, 2.5 damage = 2 damage + (0 damage or 1 damage) --> 2 damage or 3 damage
• spell power 6, 3.0 damage = 3 damage + (0 damage or 1 damage) --> 3 damage or 4 damage
• spell power 7, 3.5 damage = 3 damage + (0 damage or 1 damage) --> 3 damage or 4 damage
• spell power 8, 4.0 damage = 4 damage + (0 damage or 1 damage) --> 4 damage or 5 damage
• spell power 9, 4.5 damage = 4 damage + (0 damage or 1 damage) --> 4 damage or 5 damage
• spell power 10, 5.0 damage = 5 damage + (0 damage or 1 damage) --> 5 damage or 6 damage
• spell power 11, 5.5 damage = 5 damage + (0 damage or 1 damage) --> 5 damage or 6 damage
• spell power 12, 6.0 damage = 6 damage + (0 damage or 1 damage) --> 6 damage or 7 damage
• spell power 13, 6.5 damage = 6 damage + (0 damage or 1 damage) --> 6 damage or 7 damage
• spell power 14, 7.0 damage = 7 damage + (0 damage or 1 damage) --> 7 damage or 8 damage
• spell power 15, 7.5 damage = 7 damage + (0 damage or 1 damage) --> 7 damage or 8 damage
• spell power 16, 8.0 damage = 8 damage + (0 damage or 1 damage) --> 8 damage or 9 damage
• spell power 17, 8.5 damage = 8 damage + (0 damage or 1 damage) --> 8 damage or 9 damage
• spell power 18, 9.0 damage = 9 damage + (0 damage or 1 damage) --> 9 damage or 10 damage
• spell power 19, 9.5 damage = 9 damage + (0 damage or 1 damage) --> 9 damage or 10 damage
• spell power 20, 10.0 damage = 10 damage + (0 damage or 1 damage) --> 10 damage or 11 damage
• spell power 21, 10.5 damage = 10 damage + (0 damage or 1 damage) --> 10 damage or 11 damage
• spell power 22, 11.0 damage = 11 damage + (0 damage or 1 damage) --> 11 damage or 12 damage
• spell power 23, 11.5 damage = 11 damage + (0 damage or 1 damage) --> 11 damage or 12 damage
• spell power 24, 12.0 damage = 12 damage + (0 damage or 1 damage) --> 12 damage or 13 damage
• spell power 25, 12.5 damage = 12 damage + (0 damage or 1 damage) --> 12 damage or 13 damage
• spell power 26, 13.0 damage = 13 damage + (0 damage or 1 damage) --> 13 damage or 14 damage
• spell power 27, 13.5 damage = 13 damage + (0 damage or 1 damage) --> 13 damage or 14 damage
• spell power 28, 14.0 damage = 14 damage + (0 damage or 1 damage) --> 14 damage or 15 damage
• spell power 29, 14.5 damage = 14 damage + (0 damage or 1 damage) --> 14 damage or 15 damage
• spell power 30, 15.0 damage = 15 damage + (0 damage or 1 damage) --> 15 damage or 16 damage
• spell power 31, 15.5 damage = 15 damage + (0 damage or 1 damage) --> 15 damage or 16 damage
• spell power 32+, 16.0 damage = 16 damage + (0 damage or 1 damage) --> 16 damage

So, an average hero with a spell power of 10 will need to cast the Earthquake spell two or three times to destroy all the castle's defenses (excluding the catapult shots).
A hero will need a spell power of 22 to possibly destroy all the castle's defenses with a single Earthquake spell cast.
A hero will need a spell power of 24+ to be guaranteed to destroy all the castle's defenses with a single Earthquake spell cast.

For the Knight's castle, if the fortifications are built, the hero must have a spell power of 30 to possibly destroy all the castle's defenses with a single Earthquake spell cast.
A hero will need a spell power of 32+ to be guaranteed to destroy all the Knight's castle defenses, with the fortifications built, with a single Earthquake spell cast.

Earthquake spell damage is randomly distributed across the city's defenses.
However, as with actions during combat, this is a determined randomness, with the same actions resulting in the same damage in the same places for the city's defenses.

As walls must be destroyed from the top and not the bottom, if the Knight's castle fortifications are built, they are hit first.

The Ballista is also considered stronger than the castle's other defenses.
It is consequently more likely not to be hit directly.

All parts therefore have the same chance of being hit, these are:

• each wall fortification, if present (1 hit point)
• each wall, two parts, starting with the top of the wall (2 hit points)
• each turret (1 hit point)
• drawbridge (1 hit point)

The Ballista (1 hit point) is three times less likely to be hit.

Damage is distributed over two phases.
One point of damage is subtracted from the total damage points.
The "reduced" damage is applied, then the substracted damage point is applied.

The aim is to make it possible to hit the same portion of wall twice with the same Earthquake spell cast, so that it is less predictable in the way it hits the castle's defenses (less boring).

Here are a few examples:
Earthquake spell does 4 damage:

• 1 point of damage is subtracted from total damage points
• 3 points of damage are applied to 3 high parts of 3 walls
• 1 point of damage subtracted is applied to 1 base part of one of the three walls previously hit

Earthquake spell does 4 damage:

• 1 point of damage is subtracted from total damage points
• 3 points of damage are applied to 3 high parts of 3 walls
• 1 point of damage subtracted is applied to 1 turret

Earthquake spell does 4 damage:

• 1 point of damage is subtracted from total damage points
• 2 points of damage are applied to 2 high parts of 2 walls
• 1 point of damage is applied to the drawbridge
• 1 point of damage subtracted is applied to 1 turret

Related discussion: #7493.

This is not an option.
This can be implemented directly in fheroes2.